The aim of this study was to investigate the micro structure of the transcrystalline interphase, obtained under isothermal conditions, in polyethylene-based single-polymer microcomposites. Analysis of the angular distribution of intensity in the Xray diffraction patterns, obtained from transcrystalline layers of varying thickness, indicate that the transcrystalline growth most probably starts epitaxially with the c-axis of the orthorhombic unit cell aligned in the fiber axis direction. In the growth stage that follows, the lamellae twist as the crystals grow outward from the fiber surface, with the c-axis exhibiting variable angles with respect to the fiber axis for different transcrystalline layer thicknesses. The calculations based on the X-ray diffraction results, suggest that the pitch of the lamellar twist is 28.6 micrometers.